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This invention relates generally to fluid pumps, and particularly concerns an improved variable-displacement axial piston pump that advantageously achieves reduced auxiliary sensor fluid leakage over prolonged periods of pump operating life, and that also facilitates efficient pump assembly operations.
It has become increasingly important that the pump component of high-pressure hydraulic systems include one or more sensors that continuously monitor the status of pump operation. In the case of high-pressure hydraulic systems utilizing a variable-displacement, axial piston-type pump it is common practice to measure pump volumetric pumping rate by sensing both pump rate of rotation and pump thrust plate angular position. In addition it has been common practice to also provide the variable-displacement, axial piston-type pump component of the hydraulic system with included pressure sensors that monitor pump output (working) pressure and pump load pressure with the latter being a feedback pressure utilized for effecting control of the relative angular position of the pump thrust plate element.
Heretofore, it also has been common practice to utilize both dynamic and static resilient pressure seals in connection with mounting the different pump operating condition sensors on the pump with the dynamic resilient seals being in contact with sensor rotating elements and thus subjected to wear erosion and consequent fluid leakage over extended periods of pump operation.
It is therefore a primary objective of the present invention to provide a variable-displacement, axial piston-type hydraulic pump with an installation of multiple sensors that utilizes static resilient pressure seals exclusively.
It also is an objective of the present invention to provide a variable-displacement, axial piston-type hydraulic pump with multiple sensors that may be efficiently constructed and installed in the pump.
Other objectives of the invention will become apparent from consideration of the detailed descriptions, drawings, and claims which follow.
The instant hydraulic pump invention essentially is comprised of a conventional variable-displacement hydraulic fluid pump contained within a pump housing and of co-operating pump operating-condition sensor assemblies contained partially within the pump housing and partially within a separate position sensor housing that is removably secured to the pump housing. The hydraulic fluid pump includes multiple variable-stroke fluid-pumping pistons contained within a rotationally-driven pump barrel, an angularly-adjustable piston thrust plate co-operating with the fluid-pumping pistons to vary pump volumetric output, and various conventional internal fluid passageways.
The co-operating pump operating-condition sensor assemblies include a piston thrust plate position sensor assembly responsive to pump thrust plate position changes, a pump barrel rotational speed sensor assembly, and a pump working or output pressure sensor assembly. Advantageously, the installation of pump operating-condition sensor assemblies may optionally include a pump load feedback pressure sensor assembly. In each instance only a static (i.e., non-eroded) resilient pressure seal is utilized to seal the pump and position sensor assembly housings against fluid leakage from around the sensor body.